Work around runtime engine deficiencies.

sdk/lib/_internal/compiler/implementation/js_backend/backend.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of js_backend;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked;
 
   JavaScriptItemCompilationContext()
@@ skipping 1573 matching lines @@
       // TODO(ahe): Try to fix the enclosing element of ClosureClassElement
       // instead.
       ClosureClassElement closureClass = element;
       if (isNeededForReflection(closureClass.methodElement)) {
         return registerNameOf(element);
       }
     }
 
     return false;
   }
+
+  bool isTypedArray(TypeMask mask) {
+    // Just checking for [:TypedData:] is not sufficient, as it is an
+    // abstract class any user-defined class can implement. So we also
+    // check for the interface [JavaScriptIndexingBehavior].
+    return compiler.typedDataClass != null
+        && mask.satisfies(compiler.typedDataClass, compiler)
+        && mask.satisfies(jsIndexingBehaviorInterface, compiler);
+  }
 }
 
 /// Records that [type] is used by [user.element].
 class Dependency {
   final DartType type;
   final TreeElements user;
 
   const Dependency(this.type, this.user);
 }
 
@@ skipping 38 matching lines @@
     copy(constant.values);
     copy(constant.protoValue);
     copy(constant);
   }
 
   void visitConstructed(ConstructedConstant constant) {
     copy(constant.fields);
     copy(constant);
   }
 }